SCP-XXXX is to be kept in a containment unit of measurement 3x3x3 meters made of reinforced steel, at least two hundred (200) meters underground and five hundred (500) meters away from any other facility in the site where it is kept.

Why 3x3x3? Would containment fail if it were 4x4x4 or 2x2x2? Generally speaking, you shouldn't provide a measurement unless it is absolutely necessary for containment.
Making a room that's a perfect cube is an indicator that you just picked a number at random instead of deliberately selecting a measurement.
The whole "number (#)" thing is a Series I relic. We don't really use it anymore.

The connection to SCP-XXXX's containment unit should be rigged with explosives, which need only be detonated in the case of a Containment Breach of SCP-XXXX.

What is the connection? An underground tunnel? A road? This is important information.
Clumsy wording - try: "The connection to SCP-XXXX's containment unit is to be rigged with explosives to be detonated in the event of a containment breach".

Under any circumstance, SCP-XXXX should not be within visual range of any other SCP.

In-universe, you're not supposed to refer to an entity as an SCP. Use "object", "entity", etc.
Clumsy wording - try: "Under no circumstance is SCP-XXXX to be visually exposed to any other anomalous entity".

When entering SCP-XXXX's containment unit, SCP-XXXX should be blinded to avoid visualization of the person(s) entering its containment chamber.

Use "is to be" instead of "should be".
Repetitive wording - the first clause of the sentence is identical to the end. Try: "SCP-XXXX is to be blinded prior to an outside party entering its containment unit".

SCP-XXXX is a Caucasian Male at 1.5 meters in height, and weighing 54.4 kilograms.

It's more of a pet peeve than a serious issue, but kilograms are a measure of mass, not weight. I'd say it has a mass of 54.4 kg.

SCP-XXXX was found in [REDACTED], Ireland, portraying its abilities to its 'family', a group of individuals, who through genetic testing, were discovered not to be related not only to SCP-XXXX, but to each other as well. They were administered Class-A Amnesetics and released.

This redaction is unnecessary - I'd provide a location.
This is a run-on. I'd split it up: "SCP-XXXX was found in [REDACTED], Ireland, with a group of individuals it refers to as 'family'. Genetic testing has determined no relation between these individuals and SCP-XXXX or between each other".
Recovery and history stuff should usually go at the end of the description.

SCP-XXXX has been shown to have superhuman abilities, with enhanced strength and speed, as well as incredible endurance and stamina.

"incredible" isn't a scientific descriptor. I'd use "anomalous".

The secondary ability of SCP-XXXX is the ability to copy the abilities of other SCPs and humans.

More use of SCP as a noun.

If SCP-XXXX makes visual contact with a human or another SCP, it's eyes roll back up into its head, then quickly snap back into a forward position.

"its", not "it's".

If SCP-XXXX makes visual contact with a human or another SCP, it's eyes roll back up into its head, then quickly snap back into a forward position.

SCP as a noun.

Copied from a video recording of SCP-173

If you're going to refer to another scip, you should link to it. You can find the code for linking in the How to Write an SCP page.

Copied from SCP- 076

"SCP-076", not "SCP- 076".

Interview Log

This log would look better in block quotes. You can do this by inserting "> " at the beginning of the line you want to put in a block quote (don't include the quotation marks).

Conceptually, there are some rather significant issues to address. First off, it's a textbook case of X-Men Syndrome (I think there's actually an X-Man who can copy other people's powers, but I could be wrong). From the guide to writing humanoids, "If what's anomalous about your humanoid SCP object can be most accurately described as a voluntary "power" or "ability", you should probably start over." In this case, we have a guy with magic powers. In particular, superhuman speed and strength is a trope at this point. Copying other entities' abilities also strikes me as unoriginal - while it could be pulled off with good execution, the way it's written now kind of implies that you couldn't come up with a unique anomaly, so you made one that could be any anomaly.
Another major issue: there's no narrative. Series IV scips need a self-contained story to survive on the mainlist, and there's none of that here. Adding a narrative can often mask conceptual problems, too - SCP-3456 isn't the most original or interesting concept, but the narrative makes the entry worth reading.
If I were you, I'd start by looking for help in the Ideas and Brainstorming forum. They should be able to further refine the concept. After you do that, you should have a few narrative threads to pull, so to speak.
Hope I could help, best of luck!